Chapter 20Chapter 20Ocean BasinsOcean Basins

Section 3Section 3

Ocean-floor SedimentsOcean-floor Sediments

Notes 20-3Notes 20-3

Ocean-floor SedimentsOcean-floor Sediments

• Coarse gravel and sand are found Coarse gravel and sand are found close found close to the shoreclose found close to the shore– Heavier and harder to moveHeavier and harder to move

• Fine particles are carried farther into Fine particles are carried farther into the deep oceanthe deep ocean– Bottom sediments in deep ocean are Bottom sediments in deep ocean are

finer than sediments in shallow waterfiner than sediments in shallow water

• Core samples: drill into layers or Core samples: drill into layers or scoop up sedimentsscoop up sediments

Ocean Core SamplesOcean Core Samples

Sources of Deep Ocean Sources of Deep Ocean SedimentsSediments

• Most are made from materials that Most are made from materials that settle slowly from ocean water abovesettle slowly from ocean water above

• Inorganic SedimentsInorganic Sediments– From riversFrom rivers– Most are on the shore or continental shelfMost are on the shore or continental shelf– Occasionally they slide down the Occasionally they slide down the

continental slopecontinental slope•May move billions of kg of materialMay move billions of kg of material

•Causes turbidity currentsCauses turbidity currents

Sources of Deep Ocean Sources of Deep Ocean SedimentsSediments

• Some are from volcanic eruptionsSome are from volcanic eruptions

• Icebergs carry sediments from their Icebergs carry sediments from their place of origin across the oceanplace of origin across the ocean– As it melts the sediments fall outAs it melts the sediments fall out

• Meteorites also fall to the ocean floorMeteorites also fall to the ocean floor– Even if most of it burns up, the ash falls Even if most of it burns up, the ash falls

to the oceanto the ocean

IcebergIceberg

Sources of Deep Ocean Sources of Deep Ocean SedimentsSediments

• Organic SedimentsOrganic Sediments– Remains of marine plants or animalsRemains of marine plants or animals– Most common substances areMost common substances are

•Silica (SiOSilica (SiO44))

– Comes from microscopic organisms: Comes from microscopic organisms: radiolaria and diatomsradiolaria and diatoms

•Calcium carbonate (CaCOCalcium carbonate (CaCO33))

– Comes from the skeletons of Comes from the skeletons of foraminifera, corals and clamsforaminifera, corals and clams

RadiolariaRadiolaria

DiatomsDiatoms

ForaminiferaForaminifera

Sources of Deep Ocean Sources of Deep Ocean SedimentsSediments

• Chemical DepositsChemical Deposits– During chemical reactions solid During chemical reactions solid

materials can be formedmaterials can be formed– Nodules: lumps of mineralsNodules: lumps of minerals

•Manganese oxide, nickel oxide and Manganese oxide, nickel oxide and iron oxideiron oxide

•PhosphoritePhosphorite

Physical Classification of Physical Classification of SedimentsSediments• Two types of sedimentsTwo types of sediments

– Mud: fine silt and clay sized particlesMud: fine silt and clay sized particles

•Red clay is common on the abyssal plainRed clay is common on the abyssal plain– 40 % clay, some silt, sand ad organic 40 % clay, some silt, sand ad organic

materialmaterial– Can be gray, blue, green or yellow-brownCan be gray, blue, green or yellow-brown

– Ooze: soft, organic materialOoze: soft, organic material•40% of floor is covered with ooze40% of floor is covered with ooze

•30% of ooze is made of organic material30% of ooze is made of organic material– Diatoms, radiolaria, foraminiferaDiatoms, radiolaria, foraminifera

•Rest is mudRest is mud

Physical Classification of Physical Classification of SedimentsSediments

• Two types of ooze:Two types of ooze:– Calcareous ooze: mostly calcium Calcareous ooze: mostly calcium

carbonatecarbonate•Never found below 4,500 mNever found below 4,500 m

• It dissolves in deep, cold waterIt dissolves in deep, cold water

– Siliceous ooze: mostly silicon dioxideSiliceous ooze: mostly silicon dioxide•Comes from radiolaria and diatomsComes from radiolaria and diatoms

•Found in cold, nutrient rich ocean water Found in cold, nutrient rich ocean water (Antarctica)(Antarctica)

HomeworkHomework

Section ReviewSection Review

Pg. 401Pg. 401

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